use strict;
use warnings;
use feature qw( switch say );

sub test_it {
    my $value = shift;
    given($value) {
        when(/aaa/) { return 'wanna' } 
        when(/bbb/) { return 'be' } 
        when(/ccc/) { return 'startin' }
        default     { return 'somethin' }
    }
}
 
foreach my $str (qw[testaaa testbbb testccc testddd]) {
    say test_it($str);
}